Post by speedy1125 on Apr 26, 2011 0:00:44 GMT -5
In my almost 20 years of automotive service I never saw what just happened to me a few minutes ago!
Bear with me.......
It is important to make sure your valves are adjusted properly in order to do a proper plug read for carb tuning. Too loose and your plug will give a false rich, too tight and you will see a false lean (and it will most likely run like a turd especially if they are too tight).
I just installed a 50mm kit and have been fiddling with the carb to get the right tune. The 88 jet was too lean for sure, the 105 was way too rich but the 95 was about right, it still feels a little rich on the low end. I got a 92 to put in but before I put it in I wanted to re-adjust the valves. I have gotten pretty good at valve adjustments after owning VWs for so many years. I Put the valves on a good snug .0025 (they we just a little loose), went to put the plug back in and....OH SH!T, I felt the threads give way!
Visions of doing a plug insert went racing through my mind. Ok no big deal, I have been here before on heads that were wayyy more difficult to work on than this for sure. Once I got the plug out I looked at it to see how much debris was on it, assuming that it was the threads of the head that let go and was expecting to see lots of aluminum shavings to confirm what I suspected. I also thought, wow what a crap head since I have only done and in/out with the plug just a few times since this build 100 miles ago.
I looked at the plug and didnt see a thing. No shavings at all.
HuH?
My eyes must be getting bad but upon much closer inspection, the spark-plug actually broke and started to pull apart! This has never happened to me in all the gazillions of plugs I have changed. I have never seen it happen and have only heard of it happening once. I have seen the boot end of the plug break off, I have seen the porcelain crack due to over tightening but never this. Once I felt the plug suddenly get loose upon tightening I stopped quick and backed it out.
It was VERY difficult to see where the plug broke, I had to inspect it several times to see that it was actually broken. I cannot see down in the spark plug hole at all but I know for sure that if it had been the threads of the head that had pulled out, the plug would have been covered in shavings.
I pulled it apart for this photo because my camera is so old that I cannot get a zoom good enough to show the break.......
I am rather ashamed to admit that I only have...um...zero spare plugs on hand
Autozone is just up the street so no big deal there really.
This experience got me to thinking, When doing a sparkplug thread repair make sure to use the right type of insert. Especially on a little high compression 1 cyl. engine like these.
I am pasting the following from another site for 2 reasons...
1) Because I feel they explain it better than I can.
2) In-case the site I found it on goes poof.
"Inserts for aluminum heads are made of aluminum and are hard anodized to prevent them from ever stripping again. It is very important to understand that all coil inserts are made of stainless steel which simply transfers heat to slowly to transfer heat fast enough to allow the plug to cool and operate at the prescribed heat range. If a steel insert is used in an aluminum head it will fail to maintain metal to metal contact with the head as the engine heats up. Aluminum expands at a rate of 2.8 times more than steel. The aluminum will simply expand away from the insert and the plug will begin to loose its ability to transfer heat. If the spark plug overheats, pre-ignition and detonation can occur."
www.locknstitch.com/sparkpluginserts.htm
Also, using the proper heat range of spark-plug very important...
www.google.com/#sclient=psy&hl=en&source=hp&q=spark+plug+heat+range+comparison+chart&aq=1&aqi=g5&aql=&oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=2ec23705adf4e555
I hope this helps someone who runs into the eventual stripped spark plug hole!
Cheers friends and be safe among the scoot hunger cagers!
Bear with me.......
It is important to make sure your valves are adjusted properly in order to do a proper plug read for carb tuning. Too loose and your plug will give a false rich, too tight and you will see a false lean (and it will most likely run like a turd especially if they are too tight).
I just installed a 50mm kit and have been fiddling with the carb to get the right tune. The 88 jet was too lean for sure, the 105 was way too rich but the 95 was about right, it still feels a little rich on the low end. I got a 92 to put in but before I put it in I wanted to re-adjust the valves. I have gotten pretty good at valve adjustments after owning VWs for so many years. I Put the valves on a good snug .0025 (they we just a little loose), went to put the plug back in and....OH SH!T, I felt the threads give way!
Visions of doing a plug insert went racing through my mind. Ok no big deal, I have been here before on heads that were wayyy more difficult to work on than this for sure. Once I got the plug out I looked at it to see how much debris was on it, assuming that it was the threads of the head that let go and was expecting to see lots of aluminum shavings to confirm what I suspected. I also thought, wow what a crap head since I have only done and in/out with the plug just a few times since this build 100 miles ago.
I looked at the plug and didnt see a thing. No shavings at all.
HuH?
My eyes must be getting bad but upon much closer inspection, the spark-plug actually broke and started to pull apart! This has never happened to me in all the gazillions of plugs I have changed. I have never seen it happen and have only heard of it happening once. I have seen the boot end of the plug break off, I have seen the porcelain crack due to over tightening but never this. Once I felt the plug suddenly get loose upon tightening I stopped quick and backed it out.
It was VERY difficult to see where the plug broke, I had to inspect it several times to see that it was actually broken. I cannot see down in the spark plug hole at all but I know for sure that if it had been the threads of the head that had pulled out, the plug would have been covered in shavings.
I pulled it apart for this photo because my camera is so old that I cannot get a zoom good enough to show the break.......
I am rather ashamed to admit that I only have...um...zero spare plugs on hand
Autozone is just up the street so no big deal there really.
This experience got me to thinking, When doing a sparkplug thread repair make sure to use the right type of insert. Especially on a little high compression 1 cyl. engine like these.
I am pasting the following from another site for 2 reasons...
1) Because I feel they explain it better than I can.
2) In-case the site I found it on goes poof.
"Inserts for aluminum heads are made of aluminum and are hard anodized to prevent them from ever stripping again. It is very important to understand that all coil inserts are made of stainless steel which simply transfers heat to slowly to transfer heat fast enough to allow the plug to cool and operate at the prescribed heat range. If a steel insert is used in an aluminum head it will fail to maintain metal to metal contact with the head as the engine heats up. Aluminum expands at a rate of 2.8 times more than steel. The aluminum will simply expand away from the insert and the plug will begin to loose its ability to transfer heat. If the spark plug overheats, pre-ignition and detonation can occur."
www.locknstitch.com/sparkpluginserts.htm
Also, using the proper heat range of spark-plug very important...
www.google.com/#sclient=psy&hl=en&source=hp&q=spark+plug+heat+range+comparison+chart&aq=1&aqi=g5&aql=&oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=2ec23705adf4e555
I hope this helps someone who runs into the eventual stripped spark plug hole!
Cheers friends and be safe among the scoot hunger cagers!
lol At any rate, at least you aren't doing a thread repair job, just a plug replacement. 
